These are two different languagies.

When Russia it was formed as the state in 9 century its capital was Kiev. After dissociation the capital has been transferred in Moskow. Therefore these languages are similar. But time has established also distinctions. And Russian not always will understand Ukrainian as well as Ukrainian not always will understand Russian. I apologise for my errors :)

I'm a Russian learner!there are some different elements.but these differences are little.for example on the ticket of my friends to Kiev was written " пасажирський квиток та багажна квитанцiя". in Russian language is not "i" or word ''та''. and my friend that live in Belarus said that the first time when he was there an old man, instead of '' я говорю'' told him something like ''я ховорю ''! and she didn't understand him! l

If you speak Russian you'll be understood in many ex USSR countries . If you speak Ukrainian, you'll be understood well in Ukraine only. Russian speaking people will understand the sense but miss some words.

books say Russian, Belorussian and Ukrainian began to distinguish from one another a half of a millineum ago so they are different languages - though Russian Empire and the SU governments didn't pay much attention to it the principle language of these countries was Russian, and technically it has elaborated best of all